US2378491A - Viscosimeter - Google Patents

Description

June 19, 1945. I C E 2,378,491

VISCOSIMETER Filed April 18, 1944 Patented June 19,1945

VISCOSIMETER Bernard F. McNamee, Altadena, Calii., assignor to The Superior Oil Company, Los Angeles, Calif., a corporation of California Application April 18, 1944, Serial No. 531,537

4 Claims.

This invention relates to devices for determining the viscosity of fluids and is particularly useml in making continuous indications of the viscosity of colloidal solutions and of liquids carrying solid matter in suspension.

A general object of the invention is to provide a relatively simple and reliable apparatus for continuously indicating the viscosity of a fluid with consistent accuracy.

Another object is to provide a continuous viscosimeter capable of handling heavy. gelatinous suspensions, such as drilling mud, without clog- Fig. 3 is ahorizontal section, taken 'substan-= tially in the plane III-III of Fig. 1; and

Fig. 4 is a detail, vertical section taken in the plane IV--IV of Fig. 3.

The device shown in the drawing comprises an enclosing and supporting box or case II) within which all of the apparatus is mounted. The front wall of the case may include a window ll through which the indicating-hand and scale of the device are visible. v

The mechanism includes a tank I2 into which a liquid to be tested is continuously delivered through an inlet pipe l3 which may be connected to the source of liquid (not shown) by a flexible tube I4 extended through an aperture provided therefor in the wall of the housing. The inlet My invention is based on the phenomenon that although the flow of liquid through a tube varies inversely with the viscosity of the liquid flow through an orifice having walls of negligible length in the direction of flow is substantially independent of viscosity. To utilize this phenomenon in a practical viscosimeter, I deliver the fluid to be tested, under constant head, to two discharge nozzles, one of which is in the form of a tube of substantial length relative to its diameter, and the other of which is an orifice of negligible length compared to its diameter, and compare the rates of flow through the two nozzles. Various methods may be employed for comparing the rates of flow, but a relatively simple one is to cause the streams issuing from the respective nozzles to drive separate fluid motors which are caused to react difierentiallyjon an indicator. If the viscosity increases, the rate of flow'through the tube diminishes relative to the rate of flow through the orifice, thereby increasing the difierential force created by the two motors and causing an indicator to move in one direction. The indicator can be caused to move over a calibrated scale so as to read viscosity directly.

Referring to thedrawing:

Fig. 1 is a front elevation of a viscosilneter in accordance with the invention;

Fig. 2 is a vertical section through the device looking in the same direction as in Fig.1;

pipe I3 delivers liquid into the tank I2 tangentially, as shown in the horizontal view of Fig. 3, so as to cause the liquid to swirl in the tank and help to maintain solid materials in suspension. The inlet pipe is capable of supplying liquid faster than it is discharged from the lower part of the tank so that it continuously overflows at a lip I5 (Fig. 2), thereby maintaining a constant level in the tank. A central waste pipe I6 may be provided at the center of the bottom of the tank to drain off what sediment may settle to the bottom of the tankand thereby prevent it from accumulating in the tank and obstructing flow through the discharge nozzles.

The test discharge nozzles are two in number and comprise a hole I! in one side of the tank, which will be hereinafter referred to as the orifice, and a tube I8, which extends horizontally and radially from the tank in the opposite direction and will be hereinafter referred to as the tube, to distinguish it from the orifice I1.

As a result of the head of liquid maintained in the tank I 2, jets of the liquid are constantly discharged from the orifice I1 and the tube l8, respectively, and impinge on paddle wheels [9 and I9, respectively, which constitute fluid motors which rotate at speeds very nearly proportional to the rates of flow of liquid in the jets which impinge on them. In conformity with the flow law previously mentioned, the rate of flow through the orifice I1 remains substantially constant despite variations in the viscosity of the liquid, whereas the flow through the tube I8 diminishes noticeably witha relatively small increase in viscosity. The viscosity can therefore be measured by comparing the speed output of the paddle wheel I9 with that-of the paddle wheel' IS. A convenient way of comprising these speeds is dis- 5 closed in the drawing.

Thus, referring to Fi 3. the paddle wheel I! is mounted on a shaft 2| journaled at its opposite ends in bearings 22 and 23. On its front end the shaft 2| carries a magnet 24, the poles ofwhich are adjacent the cylindrical wall of a conductive metal cup 28 secured to a shaft 21 which is rotatably supported in a bearing 28 coaxial with the shaft 2|. The magnet 24 and the cup 25 constitute a well-known structure commonly employed in speedometers for applying a torque to one member proportional to the speed of another. In this instance the rotating magnet 24, rotating in unison with the'paddle wheel It, produces a torque on the cup 26 proportional to the speed of rotation of the magnet, this torque being in a clockwise direction. looking at the front of the device.

The other paddle wheel I9 is similarly mounted on a shaft 2| supported in bearings 22' and 23 and carries on its front end a magnet 24' cooperating with a cup 26' on a shaft 21 rotatably supported in coaxial relation with the shaft 2| by a bearing 28'. The paddle wheel l8 rotates in a direction opposite to the paddle wheel l9, and the cup 25' tends to rotate in a counterclockwise direction, looking at the front of the instrument.

In accordance with the present invention, I couple the cups 25 and 26' to each other and to an indicating hand so that the torques developed in the two cups oppose each other and move the indicator hand an amount proportional to the difference in the torque. To this end a hand 29 is fixed to a'shaft 30, the latter being journaled in a bearing 3| fixed to a wall 32 of the casing III. The rear end of the shaft has secured thereto a downwardly depending arm 34 (Fig. 1) which arm is pinned to the right end of a horizontal link 35' and the left end of a horizontally extending link 35'. The left end of the link 35 is pinned to an upwardly extending arm 36 .on the shaft 21 and the right end of the link 35 is similarly pinned to the upper end of an' arm 36' fixed to the shaft 21'. The arm 34 extends downwardly and forwardly below its point of connection to the links 35 and 35' and is connected to the inner ends of a pair of centering springs 31 and 31 which are anchored at their outer ends to pins 38 and 38' on the w n 32,,

These springs 31 and 31 retain the hand 29 in a predetermined neutral position when the opposite forces applied to the hand through the links 35 and 35' are equal, and yieldingly oppose the movement of the hand in either direction when the forces applied thereto are unequal.

As shown in Fig. 1, the hand 29 cooperates with a scale which is calibrated in opposite directions from a central zero point. This is, of course, a purely arbitrary scale and any type of scale that may be desired may be substituted for the one shown.

It is believed that the operation of the device is apparent from the description already given. However, it may be briefly summarized as follows:

The inlet pipe i 3 keeps the tank i2 filled to overflowing at the lip l5, thereby maintaining a constant level of liquid in the tank, which produces jets of liquid from the orifice l1 and the tube i8, respectively. The rate of flow through orifice I1 is substantially independent of, and

the rate of flow through tube I8 is inversely proportional to" the viscosity of the liquid. The

two Jets rotate'the paddle wheels i9 and I! in opposite directions and the paddle wheels rotate their associated magnets 24 and 24'. The rotation of each magnet produces a torque on its associated cup 25 or .26 which is proportional to its speed, and these torques are applied through arms 35 and 36', the links 35 and 35' the arm 34 and the shaft 30 to the hand 29, thereby causing it to assume a position on the scale 40 that is determined by the relative speeds of the two paddle wheels. Since the relative speeds of the paddle wheels is a function of the relative rates of flow through orifice i1 and tube l8, respectively, which in turn is a function of the viscosity of the liquid, the position of the hand 29 affords an indication of the viscosity.

Of course an important element in determining the rate of fiow through the orifice ll relative to that through the tube I8 is the pressure of the liquid in the bottom of the tank i2 and this pressure is a function not only of the depth of the liquid (which is maintained constant by the overflow lip I5), but also of the density ofthe liquid. However, variations in density produce like variations in the pressure applied to both the orifice I1 and the tube 18 so that the effect of density variations on the reading obtaincd is negligible, as compared to the effect thereon of viscosity changes.

When handling certain gelatinous solutions 0 suspensions, such as drilling mud, it is sometimes necessary to take special precautions to maintain it in liquid condition. The present apparatus lends itself to this particular purpose since it is feasible to vibrate the tank i2 and to continually wash the paddle wheels i9 and i9. Thus, as shown in Fig. 2, the tank l2 may be suspended from a, platform 4| which in turn is suspended by springs 42 from a horizontal wall 43 in the casing ID. The platform 4| has mounted thereon any suitable vibrating device, which, in this instance, is shown as an electric motor 44 having a weight 45 eccentrically secured to the motor shaft 46 so that the motor vibrates when it is energized. An arrangement of this sort sets up a very rapid, but minute, vibration of the tank l2 that is very effective in preventing fluid, such as drilling mud, from jelling. The vibration of the tank I2 is insufilcient to change its position with respect to the paddle wheels l9 and I9 enough to impair the accuracy of the instrument.

To prevent the accumulation of deposits on the paddle wheels l9 and I9, spray nozzles 41 and 41', respectively, may be mounted thereabove and supplied with water or other solvent liquid through pipes 48. A common trough 49, having a discharge spout 50 at one end, is positioned to collect the fiuid discharged from the spray nozzles 41 and 41', the orifice H, the tube i8, the sedirlnent discharge opening l6 and the overflow lip I have found that flow through the tube I8 is very nearly inversely proportional to the viscosity, so long as the velocity of the liquid therethrough is sufficiently low to produce laminar how. If the velocity of the fiuid is increased to the point where the flow becomes turbulent, the variation of the rate of flow with a change in viscosity is much less uniform. In a device of the type disclosed I have found that if the tube I8 is onehalf inch in diameter and 15 inches long, the flow remains substantially laminar for heads up to approximately 8 inches, when testing a gelatinous drilling mud.

provided with a constant head overflow 2,378,491 a specific embodiment thereof has been described in substantial detail. It is to be understood, however, that numerous changes from the exact construction disclosed will be obvious to those skilled in the art, and the invention is, therefore, to be limited only to theextent set forth in the appended claims. 1

I claim:

I. A viscosimeter for .fluids containing solid matter in suspension, comprising first and second nozzle means for discharging first and second jets, respectively, of a fluid to be tested, said respective nozzle means having flow characteristics that vary in difierent degree with changes in viscosity of the fluid, means for continuously supplying fluid to be tested to said two nozzle means at the same relative pressures, first and second fluid motor means respectively responsive to said first and second jets, and indicator means differentially responsive to said two motor tive pressures, first and second fluid motor means v means for indicating the relative rates of flow through said two nozzle means, said means for.

continuously supplying fluid to be tested to said two nozzle means comprising a tank rigidly connected to said nozzles and in fluid communication therewith, means for delivering fluid to said tank at a rate to maintain a substantially constant head for both jets, and means for vibrating said tank to agitate the fluid therein and maintain the solid matter in suspension.

2. A viscosimeter for fluids containing solid matter in suspension, comprising first and second nozzle means for discharging first and second jets, respectively, of a fluid to be tested, said respective nozzle means having flow characteristics that vary in diflerent degree with changes in Viscosity of the fluid, means for continuously supplying fluid to be tested to said two nozzle means at the same relativepressures, first-and second fluid motor means respectively responsive to said first and second Jets, and indicator means differentially responsive to 'said two motor means for indicating the relative rates oi. flow through said two nozzle means, said meansfor continuously supplying fluid'to be tested jto said nk I two nozzle means comprising a cylind and to which tank the said nozzles'are, said nozzles extending radially from the side 'wau tired."

3. A viscosimeter for fluid containing sediment,

comprisin 'st and second nozzle means for discharging first and second jets, respectively, of a fluid to be tested, said respective nozzle means having flow characteristics that vary in different degree with changes in viscosity of the fluid,

' means for continuously supplying fluid to be tested to said two nozzle means at the same relarespectively responsive to said first and second jets, and indicator means diiferentially responsive to said two motor means for indicating the relative rates of flow through said two nozzle means, said fluid motors each comprising a fiuid impelled wheel positioned in the Jet issuing from its associated nozzle.

4. A viscosimeter comprising first and second nozzle means for discharging first and second jets, respectively, of a fluid to be tested, said respective nozzle means having flow characteristics that vary in diflerent degree with changes in viscosity of the, fluid, means for continuously pplying fluid to be tested to said two nozzle means at the same relative pressures, first and second fluid motor means including motor memhas continuously rotatable in response to impingement of fluid thereon from said first and second jets, and indicator means differentially responsive to the speeds of the said two motors for indicating the relative ratesof flow through said two nozzle means, said indicator means including an indicator member with means for applying the force in one direction to said indicator, member proportional to the speed of one or said motor members, and means for applying an opposite force to said indicator member proportional to the speed of said other motor member.

BERNARD F. MCNAMEE.

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